Rare server crash when the player spawns upon connecting

On some rare occasion, the server can crash when the player spawns upon connecting due to this line: AActor *pOldCamera = p->camera;, if p->camera is a null pointer (which only seems to be the case on the server's end). This is because player_t::camera is a TObjPtr<AActor> object, and GC::ReadBarrier crashes when the object is null.

The best way to address this is to ensure that the server always initializes this pointer to nullptr because it doesn't use it for anything. Only the client needs it.